The invention relates to a means for supplying a medical instrument with rinsing fluid which is located in a container which can be put under pressure with a gas and into which two cannulas of differing lengths are inserted, wherein a short cannula can be connected via a gas conduit and a first valve to a pressurized gas source in order by way of actuation of the means at a point in time t0 to put the container under pressure by way of opening the first valve and forcing fluid from the container into a fluid conduit leading to the instrument. For deactivating the means, the fluid flow to the instrument can be interrupted by way of closing a second valve in the fluid conduit, and the pressurized gas supply to the container can be interrupted by way of closing the first valve. A sensor is provided with which the degree of filling of the container may be acquired and via which given an empty container or one which has become empty the rinsing procedure can be automatically turned off.
With TEM (transanal endoscopic microsurgery) it is necessary to unfold the rectum with CO2 gas and when required to rinse it, in order for example to rinse free the soiled optics window of an endoscope with a sterile salt solution as a rinsing fluid. The rinsing fluid is located in a container designed as a rinsing bottle, which may be impinged by pressure with the CO2 gas in order to be able to force the rinsing fluid out of the container up to the instrument. For this, for example, two cannulas are punctured through a lid or closure of the container filled with salt solution and the one cannula is connected to the pressurised gas source via a valve and the other cannula is connected to the body cavity of a patient via an endoscope or trocar sleeve.
In the course of the application it may occur that so much rinsing fluid is used that the fluid level in the container sinks below the opening of the cannula for the removal of the rinsing fluid, by which means CO2 gas gets into the body cavity and here may lead to a dangerous increases in pressure if the gas supply is not stopped in time. There are already a few devices with measures for monitoring the emptying of the container and for switching off the gas supply into the body cavity with an empty container or one which has become empty.
From the German Utility Model DE-92 07 907 U there is for example known a means with a float in the connection fittings, equipped with the cannulas, for the container or the rinsing bottle. With this the float may occlude the connection to the body cavity when the container has become empty. This principle may also be applied with the use of a suction/rinsing pump. Such means functioning with a float however require a particular connection fitting which contains the specially formed float. It is clear that this is complicated with respect to design and is therefore expensive. Furthermore for such connection fittings materials which are particularly resistant to salt solution such as stainless steel or also titanium must be used. Also such means are not optimal with respect to the hygenic demands. As a further disadvantage is also the fact that known connection fittings are complicated in their handling, and in particular when the user must first remove the closure from the rinsing means container and then must introduce and screw tight the fitting with the float means.
In the previously mentioned utility model measuring electrical solutions with position or limit value sensors are also mentioned. Apart from the costs of acquiring such optical, acoustic or capacitive sensors, means equipped with such sensors are to be seen as critical with respect to their reliability since there are numerous sources of error which cannot be excluded or only at a considerable expense. Thus, for example, the used containers or rinsing bottles have to some part extremely different wall thicknesses which may lead to errors in measurement. Furthermore, the containers often have scratches caused by their transport to the location of application, which at least with optical and capacitative sensors likewise cause errors in measurement. Particularly with optical position sensors it is also the case that these may only function without problem when they are not changed in position, which may not be ensured with every case of application. With an optical sensor the case may also arise in which a formation of drops in an already empty container is interpreted as if there were sufficient fluid present. An arrangement unchangeable in position must also be guaranteed with capacitative position sensors, since for example a change in distance of the sensor to the container will change and falsify the measuring results which are capacitatively changed. Concluding one may say of these solution principles that the position sensor for application of the manner concerned here is not suitable for the practical application, even disregarding the fact that apart from the costs of the sensor the technical expense for eliminating possible sources of error are unacceptably high.
A possible solution of the previously mentioned problems may lie in selecting the cannula diameters so small that also with an empty container and unchanged gas supply into the container and further into the body cavity, with a great probability no physiologically unacceptably high pressure would arise or no unacceptably high gas volume would get into the body cavity. With this type of flow limitation however no optimal rinsing properties arc to be achieved and by way of the gas flow which is not finished when the container has become empty there remains further a risk to the patient.
By way of the invention the cited disadvantages are to be elliminated. Thus in particular there is to be specified a means which with respect to its construction is inexpensive and with respect to its application is very simple. Furthermore the means is to be extremely secure in its function and is to offer the possibility, with an emptying of the container, of having an automatic stoppage of any gas supply to the instrument securely guaranteed and it is also prevented that containers which are inadvertently empty are put into operation.
For solving this object the initially mentioned means according to a first embodiment is formed such that the sensor is a pressure sensor acquiring the present gas pressure in the container, that in a case A on starting operation of a container sufficiently filled with rinsing fluid the temporal course of the gas pressure in the container can be acquired by way of the sensor and on ascertaining a gas pressure fall during a fixed evaluation time duration Tx the means can be deactivated. Alternatively in a case B on starting operation of an insufficiently filled or empty container the temporal course of the gas pressure in the container can be acquired by way of the sensor and after completion of a predetermined time duration Ty on ascertaining a pressure which during a fixed evaluation time duration Tz runs constant below a predetermined pressure limit value the means can be deactivated.
Another principle for solving the set object is characterised in that the sensor is a flow sensor acquiring the present gas flow in the container, that in the case A on starting operation of a container sufficiently filled with rinsing fluid the temporal course of the gas flow in the container can be acquired by way of the sensor and on ascertaining a gas flow fall during a fixed evaluation time duration Tx the means can be deactivated and that alternatively in a case B on starting operation of an insufficiently filled or empty container the temporal course of the gas flow in the container can be acquired by way of the sensor and after completion of a predetermined time duration Ty on ascertaining a gas flow which during a fixed evaluation time duration Tz runs constant below a predetermined flow limit value, the means can be deactivated.
There is provided an evaluation and control unit to which the sensor is connected and in which the output signals delivered by the sensor mathematically by differentiation may be evaluated by way of a measuring algorithm with respect to the criteria negative gradient of the gas pressure, positive gradient of the gas flow as well as constant remaining values of the gas pressure and gas flow. The mentioned unit then with the persistence of one of these four criteria over a respective predetermined evaluation time duration Ty or Tz will control the second valve for the purpose of closing or blocking the connection from the container to the instrument.
Usefully the means may be activated by actuating a foot switch which via the control and evaluation unit is in connection with an alarm device which on starting operation of an empty container with the foot switch actuation may be set into operation so that the user is immediately made aware of the fact that he must direct his attention to the container and check this whether the container is empty and is to be replaced with one filled with rinsing fluid.
Otherwise in the gas conducting leading branch between the pressurised air source and the short cannula there is connected a throttle with which the flow-through resistance of this gas conducting branch may be so adapted to the flow-through resistance of the conducting branch beginning with the long cannula and conducting rinsing fluid, that there arises a defined pressure drop and an optimisation of the measurement signal outputted by the sensor may be achieved.